The recent reintroduction of lung volume reduction surgery (LVRS) has the potential to reduce the cost of treating the advanced stages of COPD which is being investigated in a current NIH clinical trial. The purpose of this study is to test the hypothesis that LVRS will be of greatest benefit to patients with emphysematous lung destruction who have little or no peripheral airways obstruction and will be of lesser or no benefit in the cases where peripheral airways disease is a major problem. It is proposed to obtain the data needed to test this hypothesis by quantitative histological analysis of lung tissue obtained from patients entered into the LVRS clinical trial. This will allow the ranking of cases according to the severity of their airway disease, while controlling for the amount of emphysema present in the lung, and assessing this ranking against the patients' clinical outcome following surgery, which will be determined by other participants in the clinical trial. Those performing the histological analysis will have no knowledge of this outcome until all of the morphological data has been collected and submitted for analysis. The results of this study will provide definite criteria useful in selecting the patients that will receive the greatest benefit from lung volume reduction surgery.